1. Field of the Invention
This invention concerns the use of thermally expansible foaming materials, particularly thermally expansible foaming structural reinforcing materials, which are coupled to a carrier having intersecting legs to provide a reinforcing member giving additional localized stiffness to frames, rails, structure surrounding cavities, panels and other structural members. Such a reinforcing member may be useful in architectural, automotive, aviation, marine, or any other applications where increased support or stiffness would reduce vibration, noise and/or fatigue propagation, or would provide reinforcement to enhance structural strength or provide energy management during crash, crush or impact encounters.
2. Description of the Prior Art
It has long been recognized that foamable materials may be used to bond together separate components. Structural foams, urethanes, and other thermally expansible foaming materials have been used to enhance acoustic performance and provide structural rigidity. Examples of thermally expansible structural reinforcing materials used on carriers in the automotive field are illustrated in U.S. Pat. No. 5,194,199 to Thum, U.S. Pat. No. 5,344,208 to Bien et al., and U.S. Pat. Nos. 5,575,526 and 5,755,486 to Wycech. Another example of the use of thermally expansible materials on a carrier and used primarily as a baffle composition is shown in U.S. Pat. No. 5,506,025 to Otto et al. An example of the use of a foamable material on a beam-shaped structure in a piling is shown in U.S. Pat. No. 4,019,301 to Fox et al.
While such showings disclose various uses of expandable materials in reinforcing, baffling and sealant applications, there has developed a need for a simplified reinforcing member which will provide stiffening and reinforcement to a surrounding structural member. The use of expansible reinforcing materials which are initially dry and non-tacky are preferred in the manufacturing context. Such materials having shipping and handling advantages; notably this type of reinforcing material does not readily adhere to shipping containers, to workers during manufacture and installation, or to other critical surfaces which may come into contact with the material. By being non-tacky, these materials will not readily retain dirt, dust or other contaminants. Additionally, these materials will not readily adversely adhere to a carrier positioned within the structural member which helps to position the reinforcing member prior to expansion of the reinforcing material.
The reinforcing member of the present invention provides significant advantages over prior carrier and expandable material combinations in manufacturing, handling and use over prior carrier and expansible foaming reinforcing material combinations. The reinforcing member provides support to an adjacent structural member through the foamed material on the carrier, with the carrier being configured to include a mechanical fastening element to couple the expansible foaming structural reinforcing material to the carrier, with the carrier including intersecting legs for receiving the material thereon. The carrier is designed to permit the reinforcing material to foam and thereby expand upon activation to bond to two or more surfaces of the structural member to be reinforced while the material is held in place by the fastener, and may be configured to isolate the reinforcing material from some segments of the cavity within the structural member. While the carrier provides some degree of support and rigidity, further stiffening is provided by the foamed structural reinforcing material. The use of mechanical fasteners enables the initially non-tacky structural reinforcing material to be positioned in various locations and orientations whereby upon activation, the reinforcing material may foam, thereby expanding to bond the carrier to the surrounding structure. The intersecting legs of the carrier serve to support and position within a cavity or channel defined by the surrounding structural member.
Broadly speaking, the present invention includes a carrier which has two or more intersecting legs for positioning the carrier, an expansible foaming structural reinforcing material, which is preferably thermally activated, and a fastener for mechanically coupling the expansible material to the carrier prior to activation whereby after expansion, the material expands to bond together the carrier to the surrounding structural member. The legs of the carrier may be of different configurations in cross section, such as planar, arcuate, or have a combination of flat and arcuate surfaces. The fastener may be provided separately or as a part of the carrier, and preferably provides some yield or give to permit the material to shift upon impact and provide manufacturing tolerance. In one embodiment, the fastener may be provided as a synthetic resin pin passing through the material and through an opening in the carrier. In another embodiment, the fastener may be provided as a tab which may be bent to grasp the material and hold it to the carrier. The reinforcing member is typically received in a structural member such as a rail or channel which provides a cavity for receiving the structural member therein with the reinforcing material in engagement with or proximate to the structural member prior to activation.
The reinforcing material is thermally expansible, either by internally created thermal energy or by the external application of heat to activate the material. As used herein, the term xe2x80x9cthermally expansiblexe2x80x9d means to foam and thereby expand by both internally created thermal energy and the external application of heat to expand and foam the reinforcing material. The thermally expansible reinforcing material is preferably a synthetic resin-based material which foams when subjected to temperatures achieved during baking in a manufacturing process (e.g., such as during the paint and powder coat bake stage of automobile manufacturing processes). Thus, the expansion temperature of the material should be at least about 300xc2x0 F.
The foregoing advantages to the present invention will be readily appreciated by those skilled in the art with reference to the drawings and description which follow, which are intended to be exemplary rather than limiting.